The present invention relates to the field of automobile safety and relates more particularly to a gas generator comprising a neutral-thrust diffusion system.
The gas generators used in automobile safety must not become dangerous projectiles when they are initiated, although not in service, that is to say when they are being handled, transported or stored. It is therefore imperative to guarantee the optimum safety level when these generators are outside their module. This safety level can be achieved using a neutral-thrust diffusion system. This consists, for example on gas generators of tubular shape, in producing balanced radial gas outlets distributed in such a way that the forces generated upon gas liberation cancel out. The generator will thus have a neutral-thrust configuration and will present no hazard when it is initiated outside its module. However, in certain modules, in order for the airbag to inflate rapidly, it is often preferable for the gas to penetrate along a single thrust axis. To obtain this single thrust axis directed toward the airbag, a diffuser is often added which makes it possible to channel, in a single direction, the streams of gas escaping from the radial outlets of the generator. The fitting of a diffuser allows a generator with a diffusion system to remain in a neutral-thrust configuration. However, this type of module is less effective than a module using an axial-outflow generator, that is to say one that releases the gas along a single axis in the direction of the airbag.
Patent WO 93/18942 discloses a module comprising in particular a gas generator fixed to a specific structure and an airbag that can be inflated by the gas delivered by this generator.
The generator described in that patent includes a pressurized-gas reservoir and a plurality of outlet orifices arranged and distributed so as to give the generator a neutral-thrust configuration when it is not fixed onto its structure. The module also includes obturators for closing off certain outlet orifices of the generator so as to give it an axial-thrust configuration when it is attached to its structure. If, for example, the generator has two diametrically opposed orifices, one being oriented so as to be able to take the gas directly into the airbag, the other orifice will be closed off so as to give the module an axial-thrust configuration. In that document, the orifice used for inflating the airbag is also used to give the device a neutral-thrust configuration when it is initiated, although not in service. Said patent WO 93/18942 also proposes to fix the generator using the obturators. In this way, whenever the generator has to be removed from its module, it will be necessary to remove the obturators and therefore open all the radial orifices. This generator will therefore always be in a neutral-thrust configuration when it is outside its module. The systems employed in the prior art use one or more specific parts so as to obtain axial gas outflow in generators normally in a neutral-thrust configuration when they are outside their modules. These parts are, for example, the diffuser or the obturators disclosed in patent WO 93/18942.